Helminthosporium paraoligosporum Ilyukhin & Markovsk., 2023

Ilyukhin, Evgeny & Markovskaja, Svetlana, 2023, Helminthosporium paraoligosporum sp. nov., a new ascomycetous fungus from Ontario, Canada, Phytotaxa 607 (2), pp. 151-159 : 155-157

Helminthosporium paraoligosporum Ilyukhin & Markovsk. , sp. nov.

( Figure 2 ).

MycoBank number: MB843383

Etymology: —Refers to Greek prefix ‘para’ meaning ‘close’, and latin ‘oligosporum’ is the species name of Helminthosporium oligosporum .

Type: — CANADA, Ontario, Short Hills Provincial Park , 43°06’23.1”N 79°16’29.6”W, on fallen branches of Tilia sp. , 03 August 2020, E. Ilyukhin, EI-102, (BILAS 51717, holotype), ex-type culture = BILAS 51718, isotype DAOM 984992

Saprobic on branches of Tilia spp. Sexual morph: undetermined. Asexual morph: Colonies on substrate scattered, some grouped, consisted of black conidiomata. Conidiomata 0.25–1.90 mm wide, 170–750 μm high (n=10), stromatic, erumpent, hemispherical, circularly arranged, with branched, thick-walled (4–5 μm) hyphae. Conidiophores semimicronematous or micronematous, sometimes reduced to elongated conidiogenous cells 7.5–9×18–29(–37) μm (n=20), grouped, erect, cylindrical with widened base and slightly swollen apex, septate, smooth, dark brown, with apical pore. Conidia 13.5–17.5×(56–)64–76(–88) μm (n=50), clavate or obclavate, straight, some slightly curved, smooth, with 6–9 septa, dark brown, paler at apical part.

Known distribution:— Ontario, Canada.

Culture characteristics:— colonies slow-growing (16 mm) on MEA at room temperature in the dark after 14 days, initially white, with thick texture, turning pale pink, without aerial mycelium; reverse side beige. Rare pycnidia develop after 21 days of incubation, whitish to pale grey, 350–650 μm wide, solitary, mainly globose. Conidia (2.8–)3.1–3.7 × (1.0–)1.1–1.4(–1.6) μm (n = 50), 1-celled, allantoid, hyaline, smooth.

Additional specimens examined:— CANADA, Ontario, Vicinities of Welland Canal , 43°13’07.3”N 79°12’53.5”W, on branches of Tilia cordata , 16 October 2021, E. Ilyukhin, EI-418, BILAS 51719, living culture = BILAS 51720 .

Notes:— Phylogenetically, the new species is most closely related to H. oligosporum collected from Tilia spp. in different countries of Europe ( Voglmayr & Jaklitsch, 2017). Morphologically, the two species are very similar, but conidia of H. paraoligosporum (56–88 μm) appear to be slightly shorter than those of H. oligosporum (37–124 μm). The culture of P. oligosporum grown on MEA under the same conditions lacks rosy color ( Voglmayr & Jaklitsch, 2017) which also differs these two species. Morphological characteristics and phylogenetic analysis indicated that the strains EI-102 and EI-418 represent a new species in the genus Helminthosporium .

Figures

FIGURE 2. A–B. Conidiomata of H. paraoligosporum on Tilia spp.; C. 14-d old culture on MEA; D. Pycnidia formed after 21 days of incubation; E. Conidiophores; F. Conidiophore with attached conidia; G–G. Conidia. Scale bars: A–B, D = 200 μm, E= 10, F=20 μm, G–H=10 μm.